Alleles & Dominance Relationships

Flashcards covering genes, alleles, loss-of-function versus gain-of-function mutations, haplosufficiency, dominance relationships, CFTR, Mycn, and the Duffy blood group system.

Locus

The specific physical location of a gene or DNA sequence on a chromosome.

Gene

A functional DNA sequence located at a specific locus on a chromosome.

Allele

An alternative version of the same gene located at the same chromosomal locus.

Loss-of-function (LOF) mutation

A mutation that reduces or eliminates the normal function of the gene product, commonly behaving as a recessive allele relative to the wild-type allele.

Gain-of-function (GOF) mutation

A mutation that increases normal protein activity or confers a new or abnormal function, frequently behaving as a dominant allele.

Mycn

A growth-promoting transcription factor that activates genes necessary for cell-cycle progression and cell proliferation, normally regulated by phosphorylation and subsequent degradation during M phase.

Mycn T58M mutation

A gain-of-function mutation that prevents phosphorylation at Thr58, stabilizing MYCN against degradation and causing prolonged cell proliferation associated with megalencephaly syndrome and neuroblastoma.

CFTR

An epithelial membrane chloride ($\text{Cl}^-$) channel that facilitates the transport of chloride ions and water across membranes to keep mucus thin and hydrated.

Cystic fibrosis (CF)

A genetic disease caused by inheriting two nonfunctional CFTR loss-of-function alleles, resulting in disrupted ion transport and thick, sticky mucus accumulation in organs such as the lungs and pancreas.

Haplosufficiency

A condition in which a single functional copy of a gene in a heterozygote produces enough gene product to maintain the normal (wild-type) phenotype.

Haploinsufficiency

A condition in which one functional copy of a gene in a heterozygote is insufficient to produce the normal phenotype, yielding an altered or intermediate phenotype.

Incomplete dominance

An inheritance pattern in which a heterozygote displays an intermediate phenotype between the two homozygotes (such as gray color between black and white).

Null allele

A mutant allele that produces no functional gene product.

Multiple alleles

The existence of more than two allelic variants of a single gene within a population as a result of accumulated mutations, even though a diploid individual carries only two alleles.

Duffy (Fy) antigen

A protein expressed on red blood cell membranes that is utilized as a receptor by the malaria parasite Plasmodium vivax (P. vivax) to gain cellular entry.

FyBES allele

An allele of the Duffy gene containing a promoter mutation that eliminates Fy antigen expression on red blood cells, significantly reducing binding and susceptibility to P. vivax.